Outlook .pst files will not syncronizie on OneDrive

Question

Outlook .pst files will not syncronizie on OneDrive

WillJohan 50

Hi,

On my Win 11 laptop I have my .pst files in a local catalogue on my laptop. That catalogue is synchronized with OneDrive in purpose to always have a fresh copy of the files on OneDrive. However, it doesn’t seem to work (maybe as the files are open when Outlook is “open”).

When I close the Outlook program/App some of the files seem to continue to be open and the synchronization does not work.

The Outlook is a new Microsoft 365.

Anyone that can suggest a better method to have the .pst files synchronized

ChristyZhang-MSFT 26,221 Reputation points Microsoft External Staff

2023-02-01T05:36:54.64+00:00

Hi @WillJohan ,

Just checking in to see if above information was helpful. If it is useful, would you mind marking the helpful post as an answer? Which would benefit others who also has similar issues in forum.
Kathy Shattler 0 Reputation points

2023-04-22T13:53:11.4533333+00:00

So, why will my outlook.pst files only sync after I reboot my computer? I thought, and it used to be, syncing was automatic.
Jim Mills 5 Reputation points

2023-05-14T13:41:09.0266667+00:00

The file has to be closed. Plus, the file can be huge, as it stores all you mail and attachments. OneDrive also doesn't support transactional or understand the .pst is a database file. Any changes mean the whole file has to be synced. OneDrive does have differential sync to speed it up, but it doesn't do it in a database safe method. Plus, the .pst can't be shared across multiple computers without only one have it open.
Clark Thomborson 10 Reputation points

2023-05-26T04:27:49.3933333+00:00

I'm surprised that Microsoft doesn't yet special-case its handling of pst files when OneDrive is used for Backup & Restore. Oh... nevermind... that'd probably require cooperation among three devteams. The Outlook team has been transactionally updating .pst files through Exchange Server hacks for many years now. The Backup & Restore feature will, I'd guess, be handled by whatever team worked up the transactional NTFS. OneCloud would I guess be the "baby" of some other devteam - possibly on a different continent.

Now I'm wondering why this hasn't been identified as problematic until now. OneDrive has been a Backup "device" option since Win10. Hmmm... maybe it's only problematic with the latest release of O365?
Claude Ellis 0 Reputation points

2023-07-08T16:22:11.74+00:00

I am not a computer professional, but I am a computer user. The idea of backing up to the cloud on the surface seems to be a great idea as is automating syncing. But what seems to be a simple idea on the surface is actually a complicated affair. I am currently doing a system backup to OneDrive and now I cannot access my Outlook PST files. However, my Gmail account which is in Outlook does still work, The other email addresses are inoperable. I get a message that the files cannot be found. Currently, I am guessing that this is because the PST file is being uploaded to OneDrive and upon completion, all will be fine. IS THIS A CORRECT ASSUMPTION? also, my contacts seem to be gone. but as I learned from an earlier encounter setting up outlook on my new surface laptop along with WIndows 11, the address book which used to be a ".WAB" file is now integrated into the PST file.

Any comments on my situation will be appreciated
Jean-Francois Burguet 0 Reputation points

2023-09-26T14:25:57.4333333+00:00

We complement OneDrive with Veeam to copy our local .PST to a NAS
Sean McDonald 115 Reputation points

2023-12-30T14:46:30.73+00:00

I had the same issue. Here is an easy way to resolve. PAUSE OneDrive. The minimum pause is 2 hours. Close Outlook if not closed already. Wait 5 minutes. Restart (unpause) OneDrive. The PST file will sync.
Carl Anderson 0 Reputation points

2024-02-17T14:27:33.19+00:00

I have the same problem. Here is the issue. I have a file called backup.pst that my sync keeps getting stuck on. It won't let me identify where it is in my thousands of files and folders. When I search OneDrive for this "backup.pst" file it gives me matches that have nothing to do with this file name??? I have tried killing the Outlook process which should have nothing to do with a "BACKUP.pst" file????
Karen Reedy 0 Reputation points

2024-10-14T23:10:29.9933333+00:00

Works every time.
Kevin Carpenter 1 Reputation point

2025-09-24T13:35:06.9533333+00:00

I found that Excel also references the outlook.pst and had to be closed for the file to sync. It's probably the same with other integrated office apps as well.

3 answers

Your answer

ChristyZhang-MSFT 26,221 Reputation points Microsoft External Staff

2023-02-01T05:36:54.64+00:00

Hi @WillJohan ,

Just checking in to see if above information was helpful. If it is useful, would you mind marking the helpful post as an answer? Which would benefit others who also has similar issues in forum.
Kathy Shattler 0 Reputation points

2023-04-22T13:53:11.4533333+00:00

So, why will my outlook.pst files only sync after I reboot my computer? I thought, and it used to be, syncing was automatic.
Jim Mills 5 Reputation points

2023-05-14T13:41:09.0266667+00:00

The file has to be closed. Plus, the file can be huge, as it stores all you mail and attachments. OneDrive also doesn't support transactional or understand the .pst is a database file. Any changes mean the whole file has to be synced. OneDrive does have differential sync to speed it up, but it doesn't do it in a database safe method. Plus, the .pst can't be shared across multiple computers without only one have it open.
Clark Thomborson 10 Reputation points

2023-05-26T04:27:49.3933333+00:00

I'm surprised that Microsoft doesn't yet special-case its handling of pst files when OneDrive is used for Backup & Restore. Oh... nevermind... that'd probably require cooperation among three devteams. The Outlook team has been transactionally updating .pst files through Exchange Server hacks for many years now. The Backup & Restore feature will, I'd guess, be handled by whatever team worked up the transactional NTFS. OneCloud would I guess be the "baby" of some other devteam - possibly on a different continent.

Now I'm wondering why this hasn't been identified as problematic until now. OneDrive has been a Backup "device" option since Win10. Hmmm... maybe it's only problematic with the latest release of O365?
Claude Ellis 0 Reputation points

2023-07-08T16:22:11.74+00:00

I am not a computer professional, but I am a computer user. The idea of backing up to the cloud on the surface seems to be a great idea as is automating syncing. But what seems to be a simple idea on the surface is actually a complicated affair. I am currently doing a system backup to OneDrive and now I cannot access my Outlook PST files. However, my Gmail account which is in Outlook does still work, The other email addresses are inoperable. I get a message that the files cannot be found. Currently, I am guessing that this is because the PST file is being uploaded to OneDrive and upon completion, all will be fine. IS THIS A CORRECT ASSUMPTION? also, my contacts seem to be gone. but as I learned from an earlier encounter setting up outlook on my new surface laptop along with WIndows 11, the address book which used to be a ".WAB" file is now integrated into the PST file.

Any comments on my situation will be appreciated
Jean-Francois Burguet 0 Reputation points

2023-09-26T14:25:57.4333333+00:00

We complement OneDrive with Veeam to copy our local .PST to a NAS
Sean McDonald 115 Reputation points

2023-12-30T14:46:30.73+00:00

I had the same issue. Here is an easy way to resolve. PAUSE OneDrive. The minimum pause is 2 hours. Close Outlook if not closed already. Wait 5 minutes. Restart (unpause) OneDrive. The PST file will sync.
Carl Anderson 0 Reputation points

2024-02-17T14:27:33.19+00:00

I have the same problem. Here is the issue. I have a file called backup.pst that my sync keeps getting stuck on. It won't let me identify where it is in my thousands of files and folders. When I search OneDrive for this "backup.pst" file it gives me matches that have nothing to do with this file name??? I have tried killing the Outlook process which should have nothing to do with a "BACKUP.pst" file????
Karen Reedy 0 Reputation points

2024-10-14T23:10:29.9933333+00:00

Works every time.
Kevin Carpenter 1 Reputation point

2025-09-24T13:35:06.9533333+00:00

I found that Excel also references the outlook.pst and had to be closed for the file to sync. It's probably the same with other integrated office apps as well.

Answer 1

Sean McDonald 115

I have a simple solution. Close Outlook, Pause Syncing (2 hours is smallest increment), count to three, Un-Pause syncing.

Your Outlook file should upload.

Now, before you kick up and open Outlook on another computer (which I do), either logoff or shutdown the first computer. You DON'T want to have both computers logged on as there is a chance Outlook will load in the background and suddenly you will have two (2) versions of the PST file, although it will be uniquely named like "Outlook-MyComputer.pst" You will then need to figure out what is the latest Outlook file and then delete or rename the files. It is a bit of a pain.

Andy Booth 5 Reputation points

2024-12-17T09:04:20.26+00:00

Doesn't work for me, when I start my PC, outlook isnt open, but the problem is still there
Urban Andersson 1 Reputation point

2024-12-17T15:23:49.8866667+00:00

@Andy - I had that behaviour too when starting and restarting, but Seans advice to Pause and then resume synch worked for me. Thanks @Sean!
Sean McDonald 5 Reputation points

2024-12-17T16:19:06.09+00:00

It is a bit of a pain. I have two computers on different levels of the house. IF I log on to both, and do not even start Outlook, sometimes the PST file gets out of sync. Best practice is to log on to one machine, do what you need to do, close outlook, pause sync, restart sync, make sure PST file gets uploaded to One Drive, then logoff or shutdown and go to the other machine and logon and WAIT for the PST file to download.

IF the download hangs, you can always manually go online with One Drive and then download the file and drop it in the folder where you keep the PST file. I keep mine in a folder in Documents (NOT the User Profile).

What I suspect is that Windows is opening the PST file in the background if you keep your calendar in that file, which I do. It would make sense as this would be the only way you could get calendar reminders.
Simon de Labilliere 0 Reputation points

2025-03-19T10:52:36.8+00:00

Worked for me! Now if only Outlook would sync imap calendars and could get Teams to work like a functioning adult.....
Paul Bennett 0 Reputation points

2025-05-03T16:50:23.77+00:00

Great suggestion to simply pause and restart synchronization. Works every time. Thanks!

I still would like to understand why the PST file just won't sync when I close Outlook.
David P 0 Reputation points

2025-08-12T16:41:29.21+00:00

Great tip - thanks! Although fine in the past, even after a reboot my pst files have recently refused to upload to OneDrive. So I have been copying them into another folder each day so that they do upload as a backup. The "pause syncing trick" works like a charm and will save me a lot of hassle.
Sean McDonald 115 Reputation points

2025-09-07T19:10:57.79+00:00

OK, I have an update. I finally dug in and figured out what application was holding Outlook open so it could not be synced. First of all, be sure to close all your other Office Suite applications including Skype (Wait, that's gone) and Microsoft Teams.

NOW, there is one more process to deal with. It is "SearchProtocolHost.exe" Your Outlook.PST file is being indexed so that you can search the contents. If you turn off indexing of Outlook, (ControlPanel>Indexing Options) then searching your mailbox will be tedious.

I used Resource Monitor to SUSPEND "SearchProtocolHost.exe" (On CPU tab, Processes section, sort by image name and scroll down until you find "SearchProtocolHost.exe" and then right click to Suspend). That should allow Outlook to free up and Outlook.PST to sync. Alternatively, you can END TASK using Task Manager which you might be more familiar with.

So the steps are:

Close Outlook

Pause OneDrive

Kill or Suspend "SearchProtocolHost.exe"

UNpause OneDrive

NOW, every time you start Outlook back up again, at some point Indexing will startup again ("SearchProtocolHost.exe" will be spawned again) and you will have to repeat the steps above SO, wait until you see Outlook.PST is uploaded to OneDrive, then logoff or shutdown. On your other machine, DON'T open Outlook until you see the OneDrive version has synced. You MAY have to kill "SearchProtocolHost.exe" if it locked up the version of Outlook.PST on your computer BEFORE the download from OneDrive has taken place.

I hope this works for everyone.

Answer 2

Philippe Levesque 5,846 Volunteer Moderator

Hi

Outlook keep the copy open when it's open. Syncronizing PST by having outlook to directly open a file on OneDrive can lead to corruption inside your PST.

I suggest to manually copy the PST inside the OneDrive's folder when you want a copy on the cloud. That will lead to have a copy inside OneDrive's folder for backup purpose, and another's one inside your Outlook client that can stay open by Outlook.

Outlook .PST files are supported, however they are synced less frequently compared to other file types to reduce network traffic. To prevent uploading .PST files from the OneDrive sync app, read Blocking syncing of specific file types. To move .PST files out of OneDrive, read How to remove an Outlook PST data file from OneDrive. If users enable PC folder backup (Known Folder Move) manually without the group policy, they will see an error if they have a .PST file in one of their known folders (e.g. Documents). If Known Folder Move is enabled and configured via group policy, .PST files will be migrated. Outlook may show errors after .PST files are migrated because it is still looking for .PST files at original location.

CORRIE CLOETE 0 Reputation points

2023-03-04T15:09:17.91+00:00

Last Friday I received an update form Microsoft that messed up my desktop to the extent I had to take it to a technician. The computer is up and runnign again. However, since I reregistered my outlook all my emails which are saved on OneDrive don't seem to find its way back to my Outlook. Any possible solutions?
Wolf Homma 0 Reputation points

2024-05-02T20:23:55.34+00:00

So, OneDrive is too dumb to just skip the *.PST file and move on? I am glad I watched the little display in the bottom right corner of the screen that said 'uploading at 0Kb/s", otherwise I would have never known that something was wrong. No warning message like "OneDrive" stuck? Poor!
Sean McDonald 115 Reputation points

2024-05-03T14:28:50.4733333+00:00

You can exclude the PST file. OneDrive is not too dumb, it is just waiting for the file to be available for backup. This happens with any open file. The trick is to learn how to really close the PST file, which often stays open once you open Outlook. My guess is to enable calendar reminders...but that is a guess. See my suggestion below to free up the PST file. An alternative is simply to logoff and log back on. That will free up the file BUT wait for the upload before opening Outlook again or you will be chasing your tail.
Romeo Ninov 0 Reputation points

2024-08-23T05:32:50.66+00:00

@Philippe Levesque , unfortunately event if PST is outside Outlook directory it delay the sync. Maybe Microsoft can consider to add config in OneDrive to switch off this delay.

Answer 3

Niels Torp Steffensen 5

It could be because some Outlook processes still locks the PST file even after Outlook app is closed. These processes can be manually killed via Task Manager (Ctrl-Alt-Delete) or a reboot.

Sean McDonald 5 Reputation points

2024-12-17T17:20:18.29+00:00

Yeah, I have tried find that process. Outlook is easy to kill but some process is still hanging up the file. I have never been able to identify it. If you can figure it out that would be great.

Share via

Outlook .pst files will not syncronizie on OneDrive

3 answers

Your answer